3 Considerations for Designing Medical Devices to Optimize the User Experience

IF IT AIN’T BROKE, DON’T FIX IT

Technology is constantly advancing, and this presents seemingly endless opportunities to innovate patient care. But, have you ever heard the phrase “If it ain’t broke, don’t fix it”? Medical device companies, much like other manufacturing companies, can sometimes get in their own way for the sake of “innovation.” This is not to say that a company should not be attempting to improve their products through innovation. Rather, this is to say that:

Innovation should not be occurring at the expense of the usability and user experience of the device.

While technology innovation for medical devices is more visible to the public eye, improving and refining patient care and user experience along with technology is an often-overlooked critical innovation focus. It is essential because, despite the advancement in technology, the innate characteristics of humans stay the same. These innate characteristics of human users present physical, perceptual, and cognitive limitations that make them error prone, and these limitations need to be accounted for; not only device design, but extending into the design of ancillary items like instructions, packaging, and labeling. Incorporating a human-centered design approach with all aspects of their product innovation presents manufacturers additional opportunities to produce user friendly devices. With this approach, even when the device delivery system has been selected, pharmaceutical companies continue to have the opportunity to improve the user experience of their product though refinement of these ancillary items.

FEELINGS MATTER

While the usability of the device tends to primarily focus on how well the user can use the device, an evaluation of the user experience includes not only how well they were able to use the device, but also the user’s subjective feelings about their interactions (Tullis & Albert, 2013). The user experience is also driven by the aspects of the design that promote positive interactions with the device’s interface. After all, according to the aesthetic-usability effect studied by Masaaki Kurosu and Kaori Kashimura (1995), users are more likely to view more stylish or visually pleasing devices as more usable even when they are not.

The aesthetics of the device are not the most important medical aspect of the design, but it is important to know how the appearance of your design influences user perception (and, ultimately, commercial success). Placing an emphasis on maximizing the user experience and efficiency becomes more natural when the design comes from a place of empathy. An empathetic approach is when device manufacturers approach design with the goal of understanding who the intended users are and the context of the situations where the device is used. By taking an empathic approach to design, the manufacturer will strive towards promoting the user experience (technical and subjective) as well as designing a safer, more effective product. 

THREE CONSIDERATIONS

There are three important things to consider integrating during your medical device development to promote a positive user experience:

Anthropometrics

If you take a look at all of the people around you, you will notice that there is a range of sizes in the human body. People with the same height will even have differences in individual body parts. The individual differences in body sizes can present design challenges depending on the type of product being manufactured. Anthropometrics influences everything from the height of counters to aircraft cockpit design. To help understand how to take into account the differences in the human body, anthropometric measurements have been collected from both military personnel and civilian populations. Documents such as ISO 15535:2012 and ISO 7250-1:2017 provide guidance for collecting anthropometric data for databases while resources such as ANSI/AAMI HE75:2009/(R)2018 and Civilian American and European Surface Anthropometry Resource (CAESAR) provide previously collected anthropometric data. While there are extreme cases, the anthropometric measurements attempt to account for that majority of the population by creating measurements for the 5^th, 50^th, and 95^th percentile.

To effectively incorporate anthropometrics, design teams should account for the 5^th and 95^th percentile of measurements for both static and dynamic movement. While measurements taken while holding the anatomical position are important, device use also requires body movement. These anthropometric measurements can be used to evaluate current designs as well as to inform design recommendations; as inappropriate sizes will ultimately influence human performance (as seen in this example).

EXAMPLE: Imagine the following two scenarios for interacting with a push-button activated autoinjector:

Scenario 1: During an emergency allergic reaction, you are trying to give yourself an injection of epinephrine (when every second counts) with an autoinjector that is so large, it requires the use of both hands to grasp and activate the autoinjector.

Scenario 2: During an emergency allergic reaction, you are trying to give yourself an injection of epinephrine (when every second counts) with an autoinjector that allows you to grasp, uncap,  and activate the autoinjector with only one hand.

Which autoinjector would you prefer?

Using an autoinjector that fits in one hand is more manageable and less clumsy, which leads to more effective injections. A user’s ability to use an autoinjector is also influenced by how it fits in their hand, leading to how well they are able to grip the device. Biomechanical conditions for device use will improve as the size and shape of the device is designed with the user in mind. Remember, though, that context is key – Incorporating anthropometric measurements does not guarantee good design. The design team must think about why the product is being manufactured and select the measurements that provide the most accessibility to the product’s intended population.

Platform Conventions

We typically discuss the concept of platform conventions when it comes to conversations around the influence of heuristics on interface design (such as Nielsen’s 10 Usability Heuristics for User Interface Design (Stanton et al., 2013; Nielsen, 1994a; Nielsen, 1994b)). Platform conventions can refer to all aspects of the interface that people have grown accustomed to with any given product. Think about the interfaces you come into contact every day. Interfaces vary in size (e.g., smartphone versus airplane cockpit), type (e.g., touchscreen versus non-touchscreen), and industry (e.g., healthcare versus aerospace versus military). Despite these differences, the technology used is often times the same, or at the very least similar.

Imagine the following two scenarios for using an autoinjector with the activation button:

Scenario 1: Every autoinjector you have ever used for your medication has had the activation button on the top of the device. You go to use the autoinjector and based on your experience, you can probably perform the injection on autopilot. You prepare the device, see the button, follow your normal routine, and you complete the injection with no problem.

Scenario 2: Every autoinjector you have ever used for your medication has had the activation button on the top of the device. You go to use the autoinjector and use your experience with the injection process to guide your actions. You find your device and at first glance you don’t see any changes to the autoinjector so you follow your normal routine and in the process of grasping the body of the autoinjector you depress the activation button and prematurely begin the dose delivery. Upon reexamination of the device, you see that the autoinjector was updated to have activation button on the body of device instead of the top.

How well do you think you would adjust to the new location for the activation button?

The chances are that as long as the top of the autoinjector in Scenario 2 looks like a button, your first instinct will be to attempt to push it until you adapt to the button on the side. This is because the design of the product, such as a piece of an autoinjector that looks like a button, will provide the users with certain affordances which promote an expectation for how to interact with the device. 

User Feedback

User feedback can be obtained throughout the design development process. Feedback is generally collected through interviews, focus groups, and usability testing. To optimize the user experience, it is recommended that manufacturers gather feedback, 1.) early and often during the development lifecycle and 2.) within the intended use environments. Users must not only be able to use the device effectively on its own, but they must also be able to effectively use the device within the environment constraints of the intended use environments such as space limitations.  When this is done, user feedback can most accurately inform the design team about potential issues within device prototypes. If user feedback captures design flaws early in the development process, there is still an opportunity to correct those flaws and minimize the financial impact of making those changes, compared to making required changes later in the development process. 

Imagine the following two scenarios for incorporating user feedback in early device development: 

Scenario 1: Company A chooses does not place a high emphasis on obtaining user feedback in early device development stages. By the time it is at the device validation phase, the device design has received close to zero human factors integrations. The team from Company A performs the first validation study and users commit several critical use errors over the course of the study. Based on the frequency and severity of use errors, Company A must go back and complete significant revisions to the device before conducting a second product validation study. Having to complete the design revisions and the second validation study significantly delays the submission to regulatory bodies and increases time to market. 

Scenario 2: Company B places a high emphasis on obtaining user feedback early and often. As a result, Company B integrates human factors into the early stages of device development. They even perform rapid, iterative design principles for the IFU, just like Suttons Creek does! As the devices enters the validation phase, the design has undergone an iterative revisions process that included several formative usability studies. The validation study does not reveal any critical use errors, nor does Company B need to complete significant design revisions. The submission is accepted by the regulatory bodies without further requests for information. 

Which process for collecting user feedback appeals to you as the device manufacturer?

Would you prefer to dedicate a larger budget to human factors so that it can be applied throughout the design process facilitating a smoother device submission, or would you prefer to take your chances with a smaller human factors budget only to see an increase in project costs down the line related to repeat evaluations or product recalls? The more fiscally responsible path always winds up being to include human factors evaluations throughout the device development process despite the larger upfront budget. Consider the impact to your patients and even your corporate profitability if you were to retain an addition 1% of a billion dollar a year drug launch. That is $100,000,000 over 10 years! 

MAKING IT PERSONAL MAKES IT BETTER

Users enter any device interaction with their own preconceived ideas about how a device should behave, whether from the device’s affordances or past experience. Not only do they come into an interaction with their own mental models, users also face their own unique challenges based on their ability to perceive or comprehend the information presented to them. Outside of the perceptual and cognitive challenges, many users may experience physical limitations based on their body or the limitations within the environment, such as space to operate. The earlier you learn how well your intended users interact with your product, the better product you will manufacture, and the more your intended users will gravitate toward your product when it hits the market.

Using anthropometric measurements, following platform conventions, and obtaining user feedback are just a few practices that promote the user experience and usability of the device’s interface. At Suttons Creek, we utilize a number of methods to promote the usability and user experience of your interface. If you want to make sure you are investing in the most effective Human Factors program possible for your project, our team can walk you through all of the available tools and help you assess which options will be the most cost-effective paths to success.  

By: Matthew Nare, Consultant – Matthew Nare is a junior consultant on the human factors team for Suttons Creek, Inc. His previous work as a physical therapy aide provided an opportunity to gain clinical experience in inpatient and outpatient rehabilitative care settings. He came to Suttons Creek, Inc. following an internship completing clinical observational research with MedStar Health’s National Center for Human Factors in Healthcare. Additionally, he spent over a year completing accessibility evaluations at Cal State Long Beach’s Center for Usability in Design and Accessibility. This combination of work experience and his educational background provides him with a unique perspective on how the medical devices and their users function. LinkedIn: Matthew Nare

Sources:

Kurosu, M. & Kashimura, K. (1995) Apparent usability vs. inherent usability: Experimental analysis on the determinants of the apparent usability. Conference Companion on Human Factors in Computing Systems. CHI ’95. New York, NY, USA: ACM: 292-293. doi: 10.1145/223355.223680

Nielsen, J. (1994a). Heuristic evaluation. In J. Nielsen and R. L. Mack (eds), Usability Inspection Methods. New York, NY: John Wiley & Sons.

Nielsen, J. (1994b). Usability Engineering. Boston, MA: Academic Press.

Stanton, N. A., Salmon, P. M., Rafferty, L. A., Walker, G. H., Baber, C., & Jenkins, D. P. (2013). Human Factors Methods: A Practical Guide for Engineering and Design. Boca Raton, FL: CRC Press.

Tullis, T. & Albert, B. (2013). Measuring the User Experience: Collecting, Analyzing, and Presenting Usability Metrics. Waltham, MA: Elsevier, Inc.